Alarm system



Oct. 11, 1932. MlRANDA 1,881,832

ALARM SYSTEM Filed July 30, 1925 Wye/77W? Ala/7727 A. Mia/744 Patented Oct. 11, 1932 UNITED- "STATES A E T FFICE) 1MART-ILT A. MIRANDA, or ID LE VILL GE, NEw YORK, Assreuon rononivins nine,

TRIC PROTECTIVE coir trans, or New Yon-inn. Y.; A oonroner ou OF NEW YORK ALARM SYSTEM '5 which comprises a means for testing a system under various conditions.

Theinventionis particularly adapted for use in an alarm system in which tests may be made at a central station over lines exm tending to subscribers stations at a potential common to all lines re ardless of their respective lengths.

The invention relates to a normally closedv protective circuit which includes a means for 15": partially unbalacing one of the windings of i a differential relay at a subscribers station in such a manner that therelay isnot responsive to a-normally applied low potential, but

is responsive to a high potential which is im- V 26 pressed onthe line for testing purposes.

More specifically, the invention relates to the arrangement of-a shunt resistance placed acrossone of, the windings of a'difierential relay whereby the relay which is thus ren- 25 dered partially unbalanced remains inoperat-ive in the normally closed protective circuit when the normally applied low potential.

is'on the line, but with'an increase in the potential the relay becomes operative and closes 36 an operating circuit to a changer magnet which thereupon operates to bring about a desired change in the protective circuit for making a test of the condition of the system.

. Other features and advantages of the ine vention will appear from a consideration of the following description taken in conjunctionwith the accompanying drawing which shows a diagrammatic view of a circuit embodying the invention. Referring to the drawing, the main circuit includes a galvanometer 1, a low voltage battery 2, a two-way keyv 3 of the non-locking type located at the central oflice, a signaling .key 4, an alternating current ringer 5, a

E changer magnet 6, a differential relay 7, a

switch 8 arranged to set the alarm system for either a day or night period, a set of contact devices 9 for the doors and windows of the protected premises,-a' protective wiring net- 9; work 10 for doors, windows and walls,.ad-

Application filed July 30,

' syst-em'is'inoperable condition. The r1nger 5 is responsive to the operation 1925. semi m. 46,942.

justable resistances 11 and afixedresistance '13 serving as a shunt'for one ofthe' windings of the difierential r elay, and a'con- V denser 14 located at the protected pre'misesof; a subscriber. The galvanometer is furnished sea 3 for the purpose of informing the operator at;

the central office the. condition ofthe sub-j scribersline and forcontrolling' the opera tion of a drop signal and a buzzer at the cen' tra l ofiice,:'as will'hereinafter be explainefdq The low'voltage battery 2 is, provided for the normal operation of the system and thetwoway key 3 is employed as ameansfor chang- 7 ing the system fromone condition to another soa s to test the line under each; and signaling} the subscriber the'results of the testingsothat should any defects exist in the system the trouble may be remedied before the premises.

' closed for thenight and 'that thereforeit'is time to make the necessary test to's'ee ifthe of the key 3 when switchedinto the ringing] field of the other and the relay does not oper-' I ate, hen one winding however is shunted either by design'oran unauthorizedattempt to tamper with the protective circuit the relay,

is permitted to operate, therebycausingto operate the galvanometer 1', the drop 34 ,"and the buzzer 35 at the central oflice. Thedifferential relay differs fromthe ordinary type in that its right-hand winding is shunted by a res stance and it is thus rendered partially. unbalanced, but notsufficiently unbalanced as to causeoperationof thedrop signal and.

buzzerat the central oflice, while the normally applied low voltage batteryis connected to the protective circuit.

. hand winding to effect a partial unbalance,

' -The variable resistances 11 and 12, hereinafter referred to as the auxiliary and changer coils, respectively, are provided as a means for providing a definite current'fiow in the particular subscribers line; and the fixed resistance 13 is the shunt referred to above as being placed across the right-hand winding of relay-7, and is furnished for the purpose of providing an artificial error in the rightbut thisrerror, or unbalance, is not of sufficient magnitude to cause the relay to'operate when thelow potential is normally appliedto' the line; When the potential is increased, the unbalance is likewise increased and thedlfference in the current fiow through bothwindings of the relay, is raised to such an extent as to cause the relay to operate. The differential relay is arranged to be operated momentarily inasmuch as thehigh potential is applied-by key 3, whichis of the non-locking type, but it will be of suflicient duration to insure the positive operation of the changer magnet, as is particularly desired on long lines. The key 3 is so arranged that it; breaks the line for a brie'f interval when itv is released to shift from high voltage battery 15to low voltage battery 2. This break permits the armatureof the relay 7 at the subscribers station to operate thus including the network in the line again. The'purpose of operating the relay 7 is to shunt out the networkmomentarily to allow current at full strength to flow through the magnet. 6. In

this manner the operation of the magnetis always nsured.

When the system is set for its'night period,

switch 8'is in'the position shownin the drawing and the protective circuit maybe traced from the negative pole of battery 2, through the galvanometer 1, v inner right hand contacts of key 3, conductor 16, normal contacts of key 4, through ringer 5, through v the winding of changer magnet 6,.through are included in the circuit.

the left-hand winding of relay 7, next to the uppermost contact of switch. 8,.left-hand' contacts of contact devices 9, lower innermost contact of switch 8, lower arm of net work 10, through the right-hand winding of relay 7, through the variable resistances 12 and 11, upper arm of network 10, righthand contacts of contact devices 9, conductor 17, inner left-hand contacts of key 3 to ground. This circuit places the system in its. normal position, or What is commonly called a high-coil condition, that is, both the auxiliary and changer coils, connected in series, Should anyone attempt to make an unlawful entry into the protected premises during the night period by opening any of the contact devices or .65 disturbing the protective network, the normally balanced galvanometer associated with opened without breaking the circuit, the

change in resistance in the protective circuit due to the shorting out of the network would [result in an increased flow of current through the galvanometer, the movement of the pointer over to the'high contact and the operation of the drop, signal and buz zer at the central office. I i 1 When the system is set for itsday period so that the doors and windows may be opened without operating an alarm,'the switch Sis set in its alternate position and thecircuit for this periodmay be likewise traced from the central office, conductor 16, through ringer 5,. upper innermost contact of switch 8," through th elower arm of network 10, lower most contact of switch 8, through the resistance 11 and the upper arm of network 10,} nexttothe lowermost contact of switch 8, conductor 17, back to the central office' a The main circuit during the closed period is arranged to be t'estedby the operator at the central office forseveral conditions, such as high-coil, when both the auxiliary and the changer resistance coils 11 and 12, re-- spectively, are included in the circuit, lowcoil, when the changer coil 12 is shunted, and short, when the protective portion'of the main circuit is short-circuited by the opera; tion and locking of relay 7. .These three conditions provide means for the purpose of enabling the operator to determine the cur- '7 rent strength of the circuit when the resistance of said circuit is varied, the high-coil condition representingthe normal stage, low-coil condition representing the stage in which all loopsof the circuit are tested, and the short circuit condition representing a test for the proper operation of the differedtial relay.

each subscribers line is arranged to show attest reading for each of the, three coil changes and should there be any discrep ancies in any of these readings for asubscribers line under test, the operator will know that there is trouble on the line and the necessary steps can be taken to remedy it. The readings for the high and low coil l V 25 conditions of all lines are approximately the same, inasmuch as the varying lengths of the lines maybe compensated for by adjusting the resistances, such as auxiliary coil 11 and changer coil 12, which are individual; to each subscribers line. i 7

v V .The galvanometer which is individual to i I i It should be understood that the subscribers circuit is known to have a certain resistance when all the, elements including the changer coil 12 are in circuit and therefore the operator in making the high-coil test looks at the galvanometer to see if this resistance is present. Then the operator knows what the resistance of the circuit should be with the changer coil 12 short circuited, that is, the resistance of the loops, and in making the low-coil test observes the galvanometer to see if the reading is correct. The third test is merely to check up on the operation of the. differential relay. The operator knows what the galvanometer should read when the network is shorted by relay 7 and in making the last test observes the reading of the galvanometer to see if it corresponds to the known resistance. If the galvanometeron these readings does not deflect predetermined distances the operator knowsthat some part of the circuit is defective or has been tampered with and takes measures accordingly.

The changer magnet which effects the various coil standing changes is arranged to operate when the key 3 at the central office connects the high voltage battery to the main circuit. The high voltage battery which is impressed on the line causes the operation of the difierential relay, as hereinbefore stated to insure the operation of the magnet. This magnet is equipped with an armature 18 which is integral with a pivotal bar 19, eX- tending parallel to and for the full length of the core of said magnet. Atthe free endof bar 19 a pin 20 is fixedly attached for the purpose of providing a supporting means for a U-shaped member comprising two separately mounted legs 21 and 22. The legs are pivotally arranged on the pin 20 and are located thereon sufficiently apart to permit a short coil spring 23 to be mounted between them. The ends of the spring 23 are detachably secured to lugs 24 and 25 on legs 21 and 22, respectively, so that the tension in the spring tends to draw the legs togethert Disposed between the free ends of legs 21' and 22 and in engagement therewith is a ratchet wheel 26, which is loosely mounted on the magnet supporting frame (not shown). The free end of leg 21, being hook-shaped, is adapted to engage the teeth on the ratchet wheel on one side and the free end of leg 22, being pointed, is adapted to engage the teeth on the opposite side. When the armature 18 is attracted the legs 21 and 22 are drawn downward and the hook-shaped leg 21 causes the ratchet wheel to rotate one step in a counterclockwise direction, and when the armature is released the. legs 21 and 22 return to normal and the pointed leg 22 which has become locked with the ratchet wheel on its clownward movement rotates the wheel further in a counter-clockwise direction another step, so that with each rotation and release of armafashioned as to provide three sets of cam surfaces, each set consisting of three surfaces differently positioned radially, such as top, middle and bottom surfaces corresponding to the three coil conditionsof the "system,

namely, high coil, low-coil and short, as hereinbefore described. Cooperating with cam.

27 to close the necessary circuits for the three conditions in the order mentioned is a set of springmembers 28, 29 and 30, which are fixedly mounted on the magnet supporting frame (not shown), the middle member- 28 being arrangedto efl'e'ct acontact with either,

of its associated members 29 and 30 and further arranged to extend beyond its associated members to engage the surfaces ofca'm27, the point of engagement being insulated.

When the middle memberisin engagement with the middle surface of the cam,'no.con'- tact with the. associated members 29 and 30,

is effected and the system is normal, or, what is commonly called, high-coil standing, and both coils 11 and 12 are included inthe main protective circuit. When the ratchet wheel is rotated through two steps in a counterclockwise direction, the middle member engages thetop surface of the cam and thesystem is set in a low-coil condition because the middle member closes a contact withmember 29, thereby shunting the resistance coil 12 out of, the main, circuit. The cam isagain rotated in two steps and the middle member engages the ,bottom surfaceof the cam to close a contact with" member 30, which changesthe system to a short circuit condition by shunting the right-hand 'winding of thedifferential relay and causing the relay to operate and lock, thereby short-circuiting the protective portion of the" circuit.

In order to testthe system regularly, the closing time for the protected premises is usually selected for such test because at such times a-subscrib'er' should be certain that his circuit is in operable conditionbefore he locks his premises. Afterthe subscriber has closed all the circuits of his premises, the switch 8 is operated to its closed position, as shown in the drawing. The subscriber its then operates key 4, which operates galvanometer 1 and signals 34 and 35 at the central oflice to inform the operator that he desires to have his line tested. Theoperator depresses the non-locking key 3, thereby connectingthe high voltage battery 15*to the main circuit. The changer magnet 6 and differential relay 7 operate, but bothimmedi ately release. The attraction and subsequent release of the armature 18causes the cam 27' to movetwo steps so that the spring-28 engages the top, or low-coil'contact. When the its of the'cam, a circuit putting the system in low-coil standing is closed, which circuit may betraced from battery, through galvanometer 1, inner right-hand contacts of switch 3, conductor 16, normal contact of key 4;

,main circuit is closedthrough all the loops,

the galvanometer needle will deflect and show a definite change, but if this current change is not indicated, the operator .knows that some part of the circuit is open or defective. 7 WV hen the low-coil standing registers satisfactorily the operator again depresses her, key 3 to test the circuit for short standing and the second operation of this key like wise energizes magnet 6 and relay 7. i The operation and release of the magnet armature 18 moves the cam one more step to bring the bottom notch of the cam into engagement with spring member 28. This engagement causesa closure to be made between contact members 28 and 30 and shunts the right-hand winding of differential relay 7. When the low voltage battery is again brought into the circuit'diflierentialrelay 7 will lock up and shuntoutrthe protective circuit, the circuit which causes the shunting circuit to close being traceable from low voltage battery 2, gal vanometer 1, inner right-hand contacts of key 3,'conductor 16, normal contacts of key 4', through ringer 5, magnet 6 and left-hand winding of relay 7, next to the uppermost vcontact of switch 8, left-hand side of contact to thefoperator that a large current change j is efiected'and that the changer magnet and diiierential relay together with the signal I equipment in the central oifice are in operable condition. After the galvanometer needle vhas made this wide deflection, the operator depresses her key again into'the'test po sition and the cam movestwo'steps so that the spring member 28 engages the middle surface of the next, set onthe cam and the or high-coil, condition.

system is, therefore, restored to its normal, When the system is. restored to'normal the operator depresses her key 3 to ringing position so as to operate ringer 5 an arbitrary number of times to inform the subscriber thatthesystem operates satisfactorily and that he may lock his premlses. V 7

What is claimed is:

1. An alarm system comprising a normally closed protective circuit, a current measuring device thereln, protective networks and contact devices in said circuit, a low'voltage source of current normally included 1n said of current and'means to disconnect said ourrent measuring device and said low voltage source of current from said normally closed OllClllt, and to connect in to sald normally 7 closed circuit said high voltage source of current, a magnet included'in said circuit, means operated by said magnet to change the resistance of said circuit whenever the ourrent in said circuit is increased by including network measuring device, protective contactsand net- 7 works in said normally closed circuit, said circuit measuring device and alarm devices operated thereby located at said central station, a low voltage source of current normally included-in said normally closed circuit, a high voltage source of current and means for connecting said high voltage source into said normally closed circuit in place of said low voltage source, a magnet included in saidcircuit, means operated by said magnet to change the resistance of said circuit wheneverthe current in said circuit is increased by including the high voltage source in the circuit, a sensitive relay means including a coilincluded in said circuit, said relay means including contacts which are closed when the high voltage source is connected tosaid circuit and circuit means associated with said contacts and network to insure the operation of said magnet by short circuiting from said system said protective contacts and network when the contacts are closed. n 3. An alarm system'comprising a central station, a substation, a normally closed circuit including a current measuring device, protectlve contact devices and networks con-' necting said statlons, alarm devices at the source in the'circuit, sensitive relay means including a coil included in said circuit, said relay means including contacts which are closed when the high voltage source is connected to said circuit and circuit means associated with said contacts and network'to insure the operation of said magnet by short circuiting from said system said protective contact devices and network when the contacts are closed.

nected to said circuit and circuit means associated with said contacts and network to V insure the operation of said magnet by short circuiting from said system said protective contacts and network when the contacts are closed. s i s In witness whereof, I hereunto subscribe my name this 13 day of July A; D., 1925.

r MARTIN A. MIRANDA,

4:- An alarm system comprising a central station, a substation, alarm devices at the central station, protective contacts and networks at the substation connected to said devices to cause the operation of the alarm de-' vices, and a normally closed circuit connecting said stations, a source of low potential for said normally closed circuit, a source of high potential for making tests of the system, and means to connect said high potential source into the normally closed circuit in place of said low potential source, a magnet included in said circuit, means operated by said magnet to change the resistance of said circuit whenever the current in said circuit is increased by including the high voltage source in the circuit, sensitive relay means including a coilincluded in said circuit, said relay means including contacts which are closed when the high voltage source is connected to said circuit and circuit means associated with said contacts and network'to insure the operation of said magnet by short circuiting from said system said protective contacts and network when the contacts are closed.-

5. An alarm system comprising a central station, a substation, alarm devices at the central station, protective contacts and networks at the substation connected to said devices to cause the operation of the alarm devices, and a normally closed circuitconnecting said stations, a source of low potential for said normally closed circuit, a changer magnet included in said normally closed circuit to make changes in the resistance of said circuit for making tests of the system, a mag net including in said circuit, means operated by said magnet to change the resistance of said circuit whenever the current in said circuit is increased by including the high Voltage source in the circuit, sensitive relay means including a coil included in said circuit, said relay means including contacts which are closed when the high voltage source is con- 

